1. Field of the Invention
This invention relates to an apparatus and method for detecting the presence of specified molecules, and in particular to an apparatus and method for detecting the presence and/or concentrations of molecules through a barrier. The invention infers the presence or concentration of the target molecules on one side of the barrier based on an analysis of measuring molecules that have an affinity for, i.e., are attracted to or repulsed by the target molecules, and that are situated on the other side of the barrier.
Although the description of the invention refers to “molecules,” the invention is not limited to detection of molecules per se, but is broadly applicable to detection of the presence and/or concentration of constituents of molecules, including individual atoms, as well as to detection of chemical entities, both organic and inorganic, made up of molecules or groups of molecules. Furthermore, the measuring agents used to detect the presence of target entities may include constituents of molecules, including individual atoms, as well as chemical entities, both organic and inorganic, made up of molecules or groups of molecules. Therefore, while detection of molecules represents a specific embodiment of the invention, the invention in its broadest form relates to the detection and/or manipulation of target entities including chemicals, atoms, and molecules in general through a barrier, by means of complementary measuring agents also including chemicals, atoms, and molecules in general.
In one example, the invention enables blood glucose levels to be non-invasively measured by an external probe, based on changes in the orientation of glucose oxidase molecules suspended in a gel or some other gel-like viscous matrix as the probe is placed near the patient's skin. The orientation may be determined by measuring changes in an electrical property, such as resistivity, of the gel, or by detecting any other orientation-affected property of the gel or constituents of the gel, including magnetic or optical properties. The presence of target molecules may also be inferred by detecting properties of the gel that are affected by affinity-responsive properties of the molecules other than “orientation,” such as changes in migration of measuring molecules through the gel in response to an applied field.
As another example, the invention may be used to detect the presence of c-reactive protein (CRP) specific antibodies based on the orientation of CRP specific monoclonal antibodies suspended in the gel.
2. Description of Related Art
Many physiological conditions can at present only be detected by drawing blood or other fluids from a patent for in vitro analysis. Drawing blood requires a skilled practitioner, and is painful, inconvenient, costly, and poses the risk of infection. As a result, many pathologies go undetected until they are relatively advanced, while others are extremely burdensome to monitor.
An example of a disease that requires frequent withdrawal of blood for testing is diabetes. Many attempts have been made to develop a painless, non-invasive, external device to monitor glucose levels. Various approaches have included electrochemical and spectroscopic technologies, such as near-infrared spectroscopy and Raman spectroscopy. Despite extensive efforts, however, none of these methods have yielded a non-invasive device or method for the in vivo measurement of glucose that is sufficiently accurate, reliable, convenient and cost-effective for routine use.
The present invention takes a different approach to in vivo measurement of blood or tissue constituents such as glucose. Instead, of attempting to directly measure constituent concentrations, the invention utilizes the molecular or atomic forces that cause chemical interactions and reactions, referred to herein as “affinity,” to infer, based on the behavior of atoms or molecules on one side of a barrier, the presence and concentration of complementary atoms and molecules on the other side of the barrier. Such affinity forces have been studied recently with atomic force microscopy and were found capable of breaking strong chemical bonds. See, e.g., Grandbois et al., “Affinity Imaging of Red Blood Cells Using an Atomic Force Microscope,” Journal of Histochemistry and Cytochemistry, vol. 48, pp. 719-724 (May, 2000); Grubmuller et al., “Ligand Binding: Molecular Mechanics Calculation of the Streptavidin-Biotin Rupture Force,” National Library of Medicine Science, 16:271(5251:954-5 (February 1996); Moy et al., “Intermolecular Forces and Energies Between Ligands and Receptors,” National Library of Medicine, Science, 266(5183):257-9 (October, 1994); and Moy et al. “Adhesion Forces Between Individual Ligand-Receptor Pairs,” National Library of Medicine, Science, 264(5157):415-7 (April, 1994).
Chemicals or chemical constituents, including atoms and molecules, that are specifically attracted to each other will orient themselves, when in proximity to each other, in a way that maximizes the attraction (or minimizes repulsion), and will seek to eliminate such forces by combining or repelling each other in order to achieve the lowest energy state between attracted or repulsed molecular pairs. There are numerous examples of such attractive and repulsive affinity forces in nature, including formation or dissociation of compounds and explosions or implosions. The forces that result in “affinity” between molecules may be electrostatic, magnetic, nuclear, or a combination thereof, but all share the principle of seeking the lowest possible energy state for a system.
Molecular attractive forces are typically the result of complimentary electric charges exerted by the molecules on each other at chemical binding or epitope sites. Such attraction causes the molecules to orient themselves in a particular way whenever the medium in which the molecules are presents permits such orientation, so as to maximize the attractive forces among complimentary molecular pairs that are seeking to bond with each other.
In this fashion, for example, enzyme-substrate and antigen-antibody pairs “search-out” each other, and such interactive molecular search eventually culminates in molecular attachments of the molecular pairs. The prerequisite for such attachment is the proper spatial molecular orientation of the molecules in the solution. It is envisioned that the interactive molecular pairs that form such attachments must go through certain sequentially distinct steps prior to attachment. The proposed steps are as follows:    1. Molecules are dissolved in a liquid media such as water.    2. They are brought within the proximity of their complimentary molecular pairs by mixing or some other means.    3. The molecules spatially orient themselves to expose their active sites to each other.    4. The molecules then attach to each other, and consequently through attachment and reaction attain a lower energy state.
FIG. 1 is a crude illustration of the manner in which a first molecule MM attaches to a second molecule TM. The present invention is based on the principle that if one could measure either the attractive forces or the orientation of the attracted molecular pairs that are highly specific for each other, one could detect the presence of their “complimentary molecules” even before those molecules combine or react with each other. It is also based on the principle that the greater the concentration of complimentary molecules in proximity to one another, the greater the sum of the attractive force among them, in which case molecular orientation will occur more readily and at greater distances between the complimentary molecules. To date, these principles do not appear to have been exploited as a way to detect the presence and/or concentration of chemicals, molecules, or atoms across a barrier.